1. Field of the Invention
The present invention relates to a tray for growing plants, which is used for raising plant seedlings or tissue culture of plants. More particularly, the present invention relates to a tray for growing plants, which consists of a pulp mold obtained from pulp slurry by suction molding.
2. Description of the Related Art
Among trays, sheets and pots used for growing plants, trays consisting of pulp molds obtained by suction molding of pulp slurry are known. Because such pulp molds incline to be deformed, methods for preventing the deformation have been proposed.
For example, there is known a method for producing a pot sheet for growing plants, which comprises providing a male mold comprising a plurality of protrusions arranged in square and an upward bent periphery attached to an outer periphery of a flange surrounding the base portions of the protrusions arranged in square, with each protrusion consisting of a truncated cone composed of net for paper making and a projection net for paper making provided on the top of the truncated cone, overdrying a paper product on the mold, and stacking and fitting a plurality of the paper products (Japanese Patent Publication (Kokoku) No. 5-38581/1993), a plant growing bed comprising a pulp mold having a plurality of pots which are connected together at opening sides thereof and: have independent perforated bottom portions, wherein the paper mold is placed with the opening side as the under side and the bottom side as the upper side and the mold is filled with a bed material to form the bed for growing plants, and when the bed for growing plants is used for growing plants, each pot is seeded so that a plant is grown in each pot, and when each plant is transferred, the lower part of the mold for growing plants is separated so that plants were separately transferred with each pot (Japanese Patent No. 2600891) and so forth.
However, in the method of Japanese Patent Publication (Kokoku) No. 5-38581/1993, the pot sheets suffer from warpage and distortion due to moisture adsorption after drying, which degrade the dimensional accuracy. Further, it also suffers from a problem concerning mechanical strength, i.e., they cannot be transferred without a holding fixture upon transportation. The bed for growing plants of Japanese Patent No. 2600891 also suffers from insufficient dimensional accuracy and mechanical strength.
Furthermore, as a tray; using a plastic instead of pulp mold, there has been proposed a tray for growing plants which is obtained by lining up and arranging a suitable number of plant housing units made of a plastic having flexibility and elasticity in the longitudinal and transverse directions, connecting top peripheral edges of the openings of the adjoining plant housing units, and providing dish-like parts downwardly protruding at the bottom of the plant housing units, wherein the dish-like parts can freely protrude upwardly (Japanese Patent Laid-open (Kokai) No. 7-327507/1995). However, this tray for growing plants applies much load on the environment upon disposal because it uses a plastic.
Further, as a pulp mold of good dimensional accuracy, there has been proposed a pulp mold produced by wet suction molding, which includes fine fibers having 150-500% of water holding capacity defined in JAPAN TAPPI No. 26-78 (Japanese Patent Laid-open (Kokai) No. 10-311000/1998). Although use of this pulp mold is not particularly limited, it is to be mainly used as a packaging material, and use for trays for growing plants is not suggested.
The present invention was accomplished in view of the above problems, and an object is to provide a tray for growing plants composed of a pulp mold, which exhibits excellent dimensional accuracy, maintains mechanical strength in use over a long period of time, applies little load on the environment, and preferably exhibits excellent air permeability.
The inventors of the present invention assiduously studied in order to achieve the aforementioned object. As a result, they found that mechanical strength and dimensional accuracy of a tray for growing plants comprising a pulp mold can be improved by subjecting the pulp mold for the tray to hot pressing after molding, and the mechanical strength and dimensional accuracy can further be improved by adding a heat-fusible resin to a pulp slurry for the tray. Thus, they accomplished the present invention.
That is, the present invention provides the followings.
(1) A tray for growing plants, which is composed of a pulp mold obtained from pulp slurry by suction molding and hot pressing after molding.
(2) The tray for growing plants according to (1), wherein the pulp slurry contains a heat-fusible resin.
(3) The tray for growing plants according to (2), wherein the heat-fusible resin is one of resins selected from polyethylene, polypropylene, polyester, polyvinyl alcohol and acrylic resin or a mixture of two or more of them.
(4) The tray for growing plants according to any one of (1)-(3), wherein the pulp slurry contains a antifungal agent.
(5) The tray for growing plants according to any one of (1)-(4), wherein the pulp slurry contains a water repellant and/or a waterproofing agent.